Turbine bucket



Dec. 7, 1954 K. M. BARTLE-r'r v2,696,364

TURBINE BUCKET 3 Sheets-Sheet 2 Filed July 8, 1948 Kenne/z Barile# Dec. 7, 1954 K. M. BARTLETT 2,696,364

Y TURBINE BUCKET Filed July 8, 1948 3 Sheets-Sheet 3 Ifema/z Marazef 3 the cavity and the core is then invested in a wax pattern 64. The wax pattern 64, with the core embedded therein, is invested in a ceramic mold (not shown) and the wax melted out. The bucket body is then cast around and welded to the core in the usual manner and the supports 56a are ground off flush with the edges of the body.

If graphite has been used as a filler material in the core, it can be diiused into the bucket. If aluminum has been used as a filler, it may be dissolved in sodium hydroxide, and if a low melting point alloy has been used, it may be melted out of the passages.

The material of the bucket should be one having a high resistance to corrosion at high temperatures and having a high tensile strength. Suitable materials are chrome steels and cobalt base chromium, molybdenum or tungsten alloys.

After casting, if a diffusible core metal has been used, the bucket may be heat treated to diffuse the material of the core into the bucket material, thus giving a bucket of substantial uniform consistency and of high rigidity and strength.

In some instances, it may be desirable to prevent the diffusion of the core into the body metal of the bucket and if the core metal is relatively diffusible it may be coated with a relatively non-diffusible material such as another metal, a ceramic material, or the like.

Another embodiment of the present invention is shown in Figures 1l through l5 wherein a hollow core is plated around a low-melting core pattern.

Figure l1 shows a core pattern or casting 65 of lowmelting point metal, or alloy, such as Woods metal, white metal, lead solder, or the like, resting in the bottom half of a mold 66. The mold 66 is preferably made of carbon, and is suitably engraved to provide a mold for forming the casting. The casting of low-melting metal has a sprue portion 67, and a relatively heavy substantially rectangular frame or support 68 extends from the sprue to form side legs and an end leg. AA plurality of thin rounded veins or fingers 70 extend from a solid web portion 69 and in spaced relation from each other to one side leg and to the end leg of the frame 68. The web portion 69 is joined with the sprue end of the frame 68. The interior dimensions of the frame 68 are somewhat wider and longer than the dimensions of the bucket which is ultimately cast around it, as shown in Figure l5.

The casting 65 of the low melting point metal thus produced is next coated with a very thin layer of coating metal which forms the core of the finished bucket. The thickness of the metal layer is normally on the order of about 0.002 inch, and may be incorporated onto the surface of the casting by electroplating, hot dipping, or any suitable method which will deposit a thin layer of metal on the casting. The coating metal to be utllzzed is one which will not readily dissolve or disperse into the body of the metal used to form the core pattern, and will have a relatively slow rate of diffusion into the bucket metal. Suitable coating metals include nickel, cobalttungsten alloys, or the like. If desired, the casting may first be plated with a coating of nickel, followed by electroplating with chromium, to provide a nickel-chromium alloy composition plating. The sprue portion 67 may be severed from the assembly before or after the electroplating operation, as desired.

The low melting casting coated with a core metal of the type indicated is then heated to melt out the' low melting body metal, and thus produce a self-sustaining hollow core 71 shown in Figures 14 and l5. The removal of the low-melting metal provides a structure. having a wide and thin hollow inlet portion 69a feeding a plurality of hollow finger members 70a extending to one leg and an end of the hollow surrounding frame 66a. This frame portion 66a protects and holds the outer ends of the fingers 70a.

The core is then invested in wax to form the wax pattern for the bucket and may be supported 1n the wax investment mold by clamping the frame 66a between the mold sections in the same manner shown in Figure 9. The wax pattern containing the hollow core structure is then invested in a ceramic mold and the wax melted out. The bucket body is then cast around the core structure. As previously stated, the hollow fingers 70a extend to points beyond the edges of the bucket, so that when the bucket is trimmed, as shown by the chain the frame, and said core adapted 4 the vane or air foil section of the bucket and will provide passages from the hollow root, formed by the inlet 69a to two edges of the air foil.

From the foregoing description, it will be apparent that there has been provided a method of producing turbine buckets having openings therethrough for the passage of air, which method enables the bucket to be produced cheaply and which will give a more rigid bucket than may be obtained by other methods.

It is obvious that the disclosed method is subject to Various changes and modifications, and that various changes in size, shape and arrangement of parts or steps may be made without departing from the spirit of the invention or the scope of the subjoined claims.

That which is claimed as new and is desired to be secured by United States Letters Patent, is:

1. A turbine bucket which comprises a body having an anchoring root at one end thereof and a curved foil portion extending from said root, a hollow core bonded in said body having a hollow tubular end in said root portion and hollow fingers extending from said end through said foil portion, some of said fingers being curved to terminate in the trailing side edge of the foil portion, other of said fingers terminating in the end of the foil portion remote from the root, said fingers providing passages joining the root with the end and the trailing side edge of the foil portion.

2. A core for a turbine bucket which comprises a hollow metal member having a hollow substantially rectangular frame, a hollow web portion on one leg of said frame extending therefrom into the space surrounded by the frame, a plurality of hollow fingers extending from said web and terminating in two legs of the frame including an end of the frame remote from the web carrying end, said core adapted to receive body metal around the web and plurality of hollow ngers with the frame holding said fingers in proper alignment in a mold or the like.

3. A metal core for a cast hollow turbine bucket or the like which comprises a generally rectangular frame, a thin fiat hollow web extending from an end leg of said frame, a plurality of spaced hollow fingers extending from said web to the opposite end and a side edge of to be surrounded by body metal with the frame portion projecting beyond the body metal to hold the fingers and web in position in the body metal.

4. A turbine bucket comprising a bucket body portion bonded around a hollow core, said bucket body portion having fluid openings in the end and a side edge thereof, said core having a hollow root portion and a multipassaged air foil portion, the passages in said air foil portion providing fluid directing means between said hollow root and said openings on said end and side edge of said bucket body.

5. A turbine bucket comprising a bucket body portion bonded around a hollow core composed of a thin metal network, said bucket body portion having fluid openings in the end and a side edge thereof, said network having passaged root and air foil sections defining vents through the bucket body to said openings on said end and side edge of said bucket body.

6. A fluid directing member comprising a metal body having a fluid directing foil portion having fluid openings on the end and a side edge thereof and an integral root portion for attachment to a wheel or the like, said metal body being bonded around a hollow core, said hollow core having a hollow root portion and hollow fingers communicating therewith, said hollow fingers defining passages from said hollow root portion to said openings on said end and side edge of the foil portion of the metal body.

7. A turbine bucket comprising a metal body having a fluid directing foil portion and an integral root portion bonded around a thin hollow core of metal, said foil portion having fluid openings on the end and a side edge thereof, said hollow core having a hollow root portion with a plurality of hollow passages in communication with said hollow root portion defining vents from the hollow root portion to said openings on said end and liid edge of the foil portion of the metal turbine bucket 8. A fiuid directing member comprising a metal body having a fluid directing foil portion and an integral lines 72 of Figure 15, the finger members 70a lie within 85 anchoring root portion, said metal body being bonded around a hollow metal core, said hollow core including a hollow tubular portion surrounded by said anchoring root portion, laterally spaced hollow legs on the sides of said hollow tubular portion and in communication therewith extending to a transverse hollow end leg and coacting therewith to form a hollow substantially rectangular frame surrounding said foil portion, said rectangular frame having laterally spaced hollow fingers attached to said transverse end leg and to one of said side legs and extending inside said frame to said hollow tubular portion and in communication with the hollow interior thereof, some of said ngers being curved and some of said ngers terminating in a longitudinal row and some of said fingers terminating in a transverse row respectively at said one side leg and said end leg of said frame to provide a plurality of hollow passages for fluid iiow from the hollow tubular portion of the core through the foil portion of the fluid directing member.

References Cited in the le of this patent Number Number UNITED STATES PATENTS Name Date Schaper Sept. 26, 1933 Noack July 10, 1934 Darrieus Mar. 7, 1939 Faber Mar. 25, 1941 Zellbeck Sept. 29, 1942 Zellbeck Feb. 5, 1946 Hague lune 17, 1947 Fransson Mar. 21, 1950 Price Aug. 29, 1950 FOREIGN PATENTS` Country Date Germany July 29, 1905 Great Britain Jan. 17, 1947 Great Britain May 28, 1948 France Nov. 7, 1941 France Nov. 2, 1942 

